Communications cables consist of a large number of separate transmission members which make up a core. Long runs of cable in the outside plant are most conveniently realized by splicing together several lengths of cable during installation along the cable route. While the preparation and completion of the splices has traditionally been a field operation, greater splicing efficiency and reliability can be achieved with gang-type connectors installed in the factory on the cable ends, which are simply plugged in to one another in a single operation in the field. This mode of joining cable sections preferably entails a form of splice known as straight-through splicing; and thus does not contemplate the custom connecting in the field of given transmission paths. As a result, any defective transmission members such as an open copper wire in a metallic core cable, or a broken fiber of an optical fiber cable, stand a high probability of being connected into a transmission path that includes otherwise fully functional members.
Nevertheless, the delicate structure of optical fibers as well as the alignment precision required in fiber splices, make the use of factory-applied end connectors and straight-through splicing an extremely attractive expedient in the field splicing of optical fiber cables. However, any optical fiber breaks are almost always catastrophic; and thus a single break in one optical fiber in one section removes from service not only that fiber but the entire line of series-connected fibers in successive cable sections as well - although these are probably themselves intact.
The proliferating effects that broken fibers in each of several cable sections have on the efficiency of an overall cable system, are considerable. For example, a single broken fiber in each of five series-connected cable sections in a core of one hundred fibers, could render the entire system five percent unusable. In a system consisting of fifty cable sections, a break in a single fiber in each section could render the overall system up to fifty percent unusable.